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USE OF EQUIPMENT LIGHTING DURING SNOWPLOW OPERATIONS: IDENTIFIED BEST PRACTICES Laura Fay Transportation Research Board January 13, 2016 Session 818
USE OF EQUIPMENT LIGHTING
DURING SNOWPLOW
OPERATIONS: IDENTIFIED BEST
PRACTICES
Laura Fay
Transportation Research Board
January 13, 2016
Session 818
Acknowledgements
• Co-Authors – Anburaj Muthumani and
Dave Berger
• Clear Roads Technical Advisory
Committee
• Survey participants
• Mark Trennepohl and Arizona DOT
Methodology• Literature search
– Used to develop survey questions and the best
practices guide
• Agency survey
– 58 responses representing 26 states within U.S
• Operator Survey
– 369 responses representing 11 states within U.S
• Synthesis of Information
– Summary of literature search and survey findings
– Identifies the Pros and Cons, and makes
Recommendations
Introduction• The project focuses on different:
– types of light bulbs,
– color of the light,
– intensity of the light,
– mounting locations,
– flashing patterns and flashing interval,
– amperage requirements,
– mechanisms to prevent snow from blowing over the plow
onto the windshield
– mechanism to keep lights clear of snow,
– retroreflective markings,
– and day versus night settings for lights.
Auxiliary Headlights
• Typically located on the
front of snowplow
vehicles and provide
supplemental
illumination of the road
surface during plowing.
Types of Auxiliary Headlight Bulbs
• Halogen bulbs followed by LED bulbs are the most
commonly used bulb types for auxiliary headlights.
• LEDs are favored for use in new vehicles, retrofits,
and replacements due to improved visibility.
Types of Auxiliary Headlight Bulbs• Winter maintenance
agencies are moving
towards use of LEDs in
their vehicle for auxiliary
headlights.
• LED produced light
appears closer to daylight
• Energy efficient
• Long service life
• Do not produce enough
heat to melt snow
Comparison between Halogen and LEDs lights
with high and low beam (www.truckinginfo.com)
Mounting location and Beam width• Light bounce-back from auxiliary lights during snowy
conditions is a major safety issue.
• Mounting locations and beam width play a key role
in reducing light bounce-back.
• Auxiliary headlights are primarily located on:
– Truck body (most common)
– Cab hood
– Plow frame
– Others (front fenders, on the grill, and top of
headache rack)
Mounting location and Beam width
• Identified Best Practices:
– Mounting the auxiliary headlights away from operator’s
line of sight with narrow beams (spot light) helps to
reduce the light bounce-back during adverse weather
conditions.
– In particular, mounting auxiliary headlights at the lowest
possible location (above the plow or fender walls) is
recommended.
Color of Auxiliary headlight bulbs
• Recent studies did not find any significant
advantages of using yellow or any other color
lights for reducing glare during inclement weather
conditions.
• In fact, the color of headlights may have little
impact on improving visibility when compared to
improvements made by changing mounting
location and beam width during inclement weather
conditions.
Warning lights
• Warning lights typically
provide increased visibility of
the snowplow by indicating
the position and direction of
travel.
• Forward warning lights
• Rear warning lights
• Side-mount warning lights
Type of Warning light bulbs
• Agencies prefer LEDs
– reliability, improved efficiency, and reduced
maintenance costs
• LEDs lights are brighter in all observed conditions
and different light groups
• Minnesota DOT study found that LED lights
performed well, or in some cases better when
viewed directly from the rear, side, or front of the
snowplow vehicle when compared to standard HID
strobes.
– Con: Limited visibility at off angles
Color of Warning light
• Indiana DOT study found that amber is the
preferred color for all configurations followed by
bright blue for warning lights
• Snowplow operators preferred white color and
amber colored warning lights during low visibility
(e.g., fog, snow, etc.) conditions
• Lights with red, orange, and yellow color
components may have negative impacts during
blowing snow and fog conditions (Yonas and
Zimmerman, 2006)
Color of Warning light
• NDDOT believes that white color is the most
intense light to penetrate during low visibility
conditions
• NDDOT is currently testing steady burning - green
warning lights located outside the box
– To differentiate DOT vehicles from other trucks (Oil
trucks, construction trucks etc.,)
• Iowa DOT is also testing flashing blue and white
LED lights on 175 snowplow vehicles
• ODOT is using green flashing LED lights placed
atop its snowplow vehicles
Color of Warning light
The green lights demonstrated in snowy conditions on Nov. 18, 2014
(http://woodtv.com/2014/11/13/kent-co-wants-new-green-lights-for-plow-
trucks/ )
Intensity of Warning light• Agencies chose the brightest light bulb type for warning
lights, such as LEDs.
• Survey respondents indicated warning lights can never be
too bright
– Brighter lights appear to better warn drivers approaching
snowplows from the rear
– suggest having lower intensity settings especially at
night
– For vehicles to keep a reasonable distance from the
back of the snowplow vehicles
Flashing pattern and Interval• The ability of a driver to detect the presence of a snowplow
vehicle is different than the ability of the driver to detect the
relative speed of the snowplow (perceived approach).
- Flashing lights increase visibility of the snowplow for other vehicles
- Steady-burn (constant burn) lights increase the ability of drivers to
accurately perceive an approaching snowplow
• Previous studies suggest use of steady burning lights if
agencies choose only one lighting system
• Flashing lights should not be excessively brighter than steady
burning lights
Mounting location for warning lights
• Agencies are trying to mount the forward warning
lights to achieve complete visibility from the rear and
sides
• Rear warning lights are commonly flush mounted, or
mounted on a pole or telespar, single or multiple
beacons and surface mounted lights.
• Important to have a reasonable distance between
lights when using multiple colors for rear warning
lights.
Mounting location for warning lights
• NDDOT recommends
elevating rear warning
lights for increasing air
flow around lights and
reducing the snow
accumulation.
• Must be careful during
loading and unloading
operations to avoid
damaging the elevated
lights
Rear warning lights mounted on the telespars, showing snow
accumulation (NDDOT).
Proposed Mounting location for
steady burn and flashing lights
Work Lights• Work lights are floodlights or spotlights mounted at various
places on the truck exterior for illumination of specific
locations such as a wing-plow, under-body plow, top of a
truck bed, spreader-spinner, cab-steps, etc.
• Typical mounting locations of work lights identified by survey
respondents are the side and rear of the vehicles.
• LEDs and halogen bulbs are the most commonly used light
bulb for work lights
• White color is used by the majority of survey respondents
• Operators prefer additional work lights on tow plows, wing
plows, top of the cab, under body lights, top of sanders (to
keep track of materials), and some additional flood lights on
the rear.
Mechanism to Prevent Snow Blowing over
the Plow onto the Windshield• Over plow deflectors
– With trap angle less
than 50°
• Very few survey
respondents have
over-plow deflectors
on their vehicles
• Other options - air
foils or bug shields.
Mechanism to Keep Lights Clear of
Snow
• LEDs accumulate more snow than other light bulbs
Comparison of snow accumulation between standard strobe (left) and
Whelen LED (right) after heavy snow conditions (Vogt and Miller, 2008).
Mechanism to Keep Lights Clear of
Snow• Wind deflectors mounted above the box of the snowplow were
recommended to keep the rear warning lights free from snow build-up
• Air foils have been found to be effective in keeping the rear of vehicles
clear of snow
• Iowa DOT recommended the use of “scoop” tailgate deflectors to
decrease the amount of snow on the back of vehicles
• Wind deflectors may not be effective for tail lights and brake lights
Airfoil test run – without
airfoil showing more snow
accumulation on the rear
(left); with airfoil showing
less snow accumulation on
the rear (right) (Nevada
DOT, 2015).
Mechanism to Keep Lights Clear of
Snow• Nevada DOT suggested the feasibility of thin sheet
heaters powered by a 12 volt source to be used on
snowplow lights
• Heated lenses need a control switch
• In cold snow events (around 15°F), heated lenses can
create a dome of ice over the LED lens
• Alter the mounting locations of lights to enhance air
flow around the lights.
Retro-reflective Markings
• Retro-reflective markings increase the visibility of the
vehicle at night and during low-light conditions.
• Retro-reflective materials become completely
ineffective if covered by snow and or dirt.
• The biggest issues with retro-reflective markings is
keeping them 100% clean
• Most commonly used color combinations for
reflective markings are red and white
Day Versus Night Settings
• The combination of more light sources and higher
intensities may temporarily blind approaching vehicle
drivers especially during nighttime operations
• Studies recommended using different intensity
lighting for daytime and nighttime operations
• Day-versus-night time settings are not a commonly
available feature in snowplow vehicles
• Very few respondents have manually operated day-
versus-night light settings on their vehicles
Case Example – ADOT
• LED prototype front plow auxiliary lighting used on truck with
58” front plow.
• All lights are LED, cost to up fit with this package was $3K.
• This truck was up fit with 100% LED lights in summer of 2014.
– Winter 2014/2015 was relatively mild with few significant snow
events. Therefore we’ve not fully tested this set up.
• Initially, the operators like the visibility provided by this lighting,
but due to being in the drivers direct line of sight, bounce back
is an issue.
KC 1668 HID Fog
Lamp, 50 watt,
305,000 candlepower
KC 1851 HID Fog Lamp,
35 watt, 350,000 beam
candlepower
Truck-Lite 27270C 7
Round LED Headlamp,
2 LED Arrays Multi-volt,
@ 12.8v operation, high
beam function draws
3.60a, low beam function
draws 1.80a 1,300
Lumens
Equipment and Labor Costs
• 7 in LED clear flood light (2) $641.66
• 5x7 in LED clear kit light (1) $845.07
• 7 in LED clear spot light (2) $665.96
• Labor 11.5 hrs $753.25
• Total Costs for upgrade: $2919.94
Plow Driver Survey• Light bounce back and scatter was rated better
(6/10) with the new set up.
– Driver comment: the lower the mounting or off to
the passenger side the lights are the better.
• Driver visibility was also rated better (7.5/10)
– Driver comments: if we can get the heated lenses
on the LED lights as you have to stop frequently to
clear snow and ice off.
• Effects of plow lights to oncoming traffic
– Driver comments: Were not bad, but adjusted lights
anyway toward the fog line, away from oncoming
traffic.
Plow Driver Survey• Overall rating for lighting package: 8/10
– The only recommended change is to include the
heated lens on the LED fender mounted lights
• Rated each lighting type:
– Fender mounted HID 6” fog: 8.5/10, don’t freeze up
and seem to cut through the snow well.
– Fender mounted LED: 4.5/10, because of the icing
issue if they were heated I would rate them a lot
higher.
– Plow frame mounted HID 8” fog: 8.5/10, cut through
the snow and do not ice up.
• Testing this year in moderate snow and heavy
fog driver found:
– Used the plow light shut off switch frequently,
except during night time clean-up activities.
*Based on its success, AzDOT is wondering if they
should add on-off switches to all of their plows.
2013 model plow truck
retrofitted with 100%
LED plow lights and
installed a switch in the
cab that shuts off the
driver side lights.
Conclusions
• Halogen bulbs followed by LED bulbs are the most
commonly used bulb types for auxiliary headlights.
LEDs are favored for use in new vehicles, retrofits,
and replacements due to improved visibility.
• Mounting the auxiliary headlights away from the
snowplow operators line of sight with narrow beams
(spot light) helps to reduce the light bounce-back
during adverse weather conditions. In particular,
mounting auxiliary headlights at the lowest possible
location (above the plow or fender walls) is
recommended.
Conclusions
• With the emergence of LEDs for auxiliary headlights,
warning lights, and work lights, it is important to have
some mechanism to keep the lights clear of snow
because LEDs do not produce enough heat to melt
snow and ice off the light surface.
• Over- plow deflectors have been found to be
effective in keeping the front grill clear of snow.
Conclusions
• Amber is the color most commonly used for warning
lights. However, agencies are using and/or testing
blue, white, and green colors. Operators prefer white
colored warning lights because of perceived
increased conspicuity during low visibility (e.g., fog,
storm conditions, etc.) conditions.
• It is important to have both flashing lights and steady
burning (constant burn) lights that are spaced apart
for rear warning lights. Flashing lights help to identify
the presence of a plow and steady burn lights aid in
the estimation of the relative speed of plow.
Conclusions
• Retro-reflective tape markings are very effective and
provide an additional level of warning for
approaching vehicles. However, keeping retro-
reflective markings clear of snow and visible at all
times is an issue during snow plowing operations.
• A combination of wind deflectors and heated lens
can be used to keep the warning lights and retro-
reflective tape clear of snow. However, it is important
to have a control switch that can turn on and off the
heated lenses based on the conditions.
Conclusions
• The issue of increased brightness introduced by
warning lights can be resolved by using day-versus-
night settings for lights on snowplow vehicles, but
this feature is not commonly available.
Questions?
Final Report can be found here:
http://clearroads.org/project/use-of-equipment-
lighting-during-snowplow-operations/
Laura Fay
Western Transportation Institute
